The goal of the proposed research is the characterization of the opiate receptor and the elucidation of the molecular mechanism of opiate action. The opiate receptor is a membrane-associated proteinaceous structure present in mammalian nervous tissue and provides the site of action for opiates and also endogenous peptides, possibly neurotransmitters or hormones involved in pain perception. Studies of the solubilized receptor will emphasize the structural features of the opiate binding site including size, subunit composition, conformation, and mechanism of action. Characterization of active receptors and of solubilized covalent enkephalin-receptor complexes from a variety of nervous tisues will be emphasized using molecular exclusion chromatography and polyacrylamide gel electrophoresis. In vitro binding studies of the membrane-bound receptor will be used to investigate regulation by sodium and guanyl nucleotides and conformational states in both naive and drug-dependent tissue. In addition, in vitro binding studies involving (3H) cyclazocine (Proposed Mug, K, and Sigma ligand), (3H) ethylketocyclazocine (Mu and K ligand), and (3H) SKF-10,047 (Mu and Sigma ligand) will be used to obtain biochemical substantiation for the putative K and opiate receptor subclasses. Such studies are hoped to contribute significantly to the understanding of how the brain works with regard to pain perception and endogenous psychosis and how, on the molecular level, opiates and opioid peptides exert their physiological effects including tolerance. Such an understanding of narcotic action should expedite the design of therapeutic agents which are strong analgesics but do not produce dependence, and facilitate the production and use of agents of value in the therapy of patients dependent upon narcotic drugs.